1. Field of the Invention
The present invention relates to a recording method and material. More particularly, it relates to a recording method and material employing a color former which forms a clear color image by adsorption on or reaction with a cellulose fiber.
2. Description of the Prior Art
Heretofore, recording materials which actually utilize a color former include a pressure-sensitive recording paper (e.g., as disclosed in U.S. Pat. Nos. 2,505,470, 2,505,489, 2,550,471, 2,548,366, 2,712,507, 2,730,456, 2,730,457, 3,418,250, etc.) and a heat-sensitive recording paper (e.g., as described in Japanese Patent Publication No. 4,160/68; U.S. Pat. No. 2,939,009, etc.). In these cases, to obtain a recording image, a colorless or a substantially colorless electron-donating organic compound (hereinafter designated "color former") is changed to a colored species by adsorption or reaction, and an acid reactive inorganic or organic acid electron-accepting material (hereinafter designated "developer") having capability to form a clear color image is required.
In addition, a recording or printing method which produces a color image by supplying an ink containing a color former onto a recording sheet coated with a developer thereon through a medium such as a felt pen or a stencil (e.g., as described in German Patent Application No. OLS 1,939,624 and Japanese Patent Publication No. 28,129/73), is known.
Further, a method for obtaining a color image by contacting a crayon-type color former onto a recording sheet coated with a developer is known.
In most cases, the color forming phenomenon of the color former as described above requires a physical stimulus such as the application of a pressure with a pen, typewriter, or the like, application of heat, etc.
Of these, a pressure-sensitive copying paper is the most representative form. A pressure-sensitive copying paper comprises a combination of a capsule-coated sheet which is a sheet on which is coated isolated liquid droplets contained in microcapsules containing a color former dissolved in a water-insoluble organic solvent, that is, a color former dissolving oil, and a developer sheet which is a sheet on which is coated an acid reactive material which forms a color image by reacting with the color former. To obtain a copied image, the capsule-coated paper is superposed on the developer sheet so that the capsule-coated surface can contact the developer coated surface, and then a localized pressure is applied using a pen, typewriter, etc. At this moment, the capsules are ruptured and the color former containing oil released from the capsules contacts the developer layer, and the color former and the developer react to form a densely colored copied image.
Further, according to another embodiment of a pressure-sensitive copying paper in practical use, the microcapsules encapsulating the color former containing oil and the developer are separately coated on opposite surface of the retaining sheet, or in one layer or two or more layers on the same surface of the sheet.
Heretofore, color formers used for the pressure-sensitive copying papers and other recording materials include Crystal Violet lactone, Benzoyl Leuco Methylene Blue, 3-diethylamino-7-dibenzylaminofluoran, 3-methyl-2,2-spirobi(benzo [f]-chromene), etc. When these color formers are used, acid reactive organic or inorganic acid materials, that is, developers are necessary, as has already been described, to obtain recorded images. Typical developers include clay minerals such as terra abla, activated clay, attapulgite, a condensate of phenol and formaldehyde, a phenol compound, aluminum salt, zinc salt, or magnesium salt of a salicylic acid derivative, a phenolate of aluminum, zinc, or magnesium, etc.
Since known recording materials require coating of color formers to obtain color images, the following disadvantages arise.
1. The paper coated with the color former differs from the uncoated paper, and printability is poor as compared with a high quality paper. That is, the clay mineral developer coated sheet, as compared with usual papers for printing, easily causes clogging of the printing plate in long-run printing. Also, a phenol-formaldehyde resin coated paper has a difficulty in that the drying speed of an ink after printing is somewhat slower.
2. Since the active surface of the developer sheet generally is stored uncovered and in contact with the air, a decrease of developing ability due to contamination by adsorption, etc., and yellowing of the developer sheet surface due to light are inevitable.
3. A coating procedure is necessary to coat the developer. In paper manufacturing, coating with a size press can be used, however, such a coating is not practical due to the poor color image density obtained when known color formers are used.
Considering the above descriptions, it can be understood that, if the use of special developers were to become unnecessary in recording materials utilizing the color forming reaction of color formers, the above-described disadvantages would all be removed.